visitTree

The visit tree method, visit tree walks over a subtree and processes
the callback object to perform some operation on the subtree

there are some details in the implementation which according to the spec have
to be in place:
a) before calling the callback and traversing into the subtree pushComponentToEL
has to be called
b) after the processing popComponentFromEL has to be performed to remove the component
from the el

The tree traversal optimizations are located in the visit context and can be replaced
via the VisitContextFactory in the faces-config factory section